Telephone bepeatee



Nov. 20 1923.

O. B. BLACKWELL TELEPHONE REPEATER Filed May 29, 1919 INVENTOR. 7 (1B.Blackwell BY C A TTORNIJ Patented Nov. 20, 1923.

UNITED STATES PATENT OFFICE.

OTTO B. BLAGKWELL, 0F GARDEN CITY, NEW YORK, ASSIGNOR 'lO AMERICAN TELE-PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

TELEPI-IUNE REPEATER.

Application filed may 29, 1319. Serial No. 300,558.

To all rv/1 0 m it may concern:

Be it lznown that l, Or'ro l3. BLAonwnLL, residing at titarden City, inthe county of Nassau and State of New York, have invented certainImprovements in Telephone Repeaters, of which the following is aspecilication.

This invention relates to telephone repeaters and more particularly torepeaters for phantomed transmission systems.

Tn systems of this character it is common practice to separate thephantom from the side circuit current at repeater installations by meansof a pair of repeating coils or transformers, in each side circuit. Thephantom current is led from the midpoints of these coils to the repeaterof the phantom circuit, and the side circuit currents are con ducted tothe side repeaters by connections to the secondary winding of the coils.The metallic continuity of the line conductors is thus interrupted atthe repeating coils. so that telegraph current or other direct currentfor signaling purposes cannot be sent over the line, without the use ofauxiliary apparatus for shunting the current around the repeaterinstallation. Such apparatus must also be provided for alternating signaling currents of low frequencies, because of the low efficiency of thetransformers and other repeater apparatus when traversed by suchcurrents.

The essence of the present invention is the elimination of the abovedescribed repeating coils and the preservation of the conductivecontinuity of the line conductors, so that the auxiliary apparatus fortransmitting telegraph and other signaling currents may be dispensedwith. This is accomplished by the use of a transformer having the coilsof one winding inserted in th line conductors, and the coils of theother winding associated with one side, either input or output, of theamplifying device. The other side of the amplifying device is associatedwith the line conductors by means of a secon d transformer connectedbetween the midpoints of inductance coils or like devices bridged acrossthe side circuits. The coils of the first transformer are so connectedthat it responds to phantom current but not to side current and thesecond transformer receives only phantom current by virtue of itsbalanced connections to the line. Side current is thus excluded from theamplifyng device.

; The inductance devices which s rve to associate one of the abovetransformers with. the phantom circuit may serve also to associate theside repeaters with the side circuits.

A good understanding of the invention may be had by considering thefollowing detailed description, with reference to the accompanyingdrawing which, in diagrammatic form, shows an arrangement of circuitsand apparatus embodying this invenlion.

In this drawing reference characters 1, 2, 3 and 4: designate the lineconductors of a four-wire phantom group. The conductors l. and 2 aretraversed in opposite directions by current of one side circuit and theconductors 3 and ll, by current of the other side circuit. Phantomcurrent flows in one dire. tion through conductors l and 2 in parallel,and in the other direction, through conductors 3 and 4:, in parallel.

A transformer 15 is shunted across each side circuit at points 50 and 51on the line conductors, and the midpoints 52 and 53 of thesetransformers are connected to the terminals of a transformer 21. Abridge is thus established across the phantom circuit, and phantomcurrent flows through this bridge from one side of the phantom circuitto the other. This current traverses half of the winding of eachtransformer 15 in opposite directions but flows through both halves oftransformer 21 in the same direction. It has therefore no magnetizingeffect on transformers 15, but it does create a flux in transformer 21,so that this transformer impresses the phantom current on the amplifyingdevice 40. This device may be of any suitable type and preferablycomprises an electron tube, the grid, filament and plate circuits ofwhich may be connected in the usual manner. The outgut circuit of thisamplifying device is associated with the primary winding of atransformer 20, comprising coils 33 and 34 connected in series. Thesecondary winding of this transformer is comprised of coils 25 to 32, apair of these coils being inserted in each line conductor. The coils ofeach winding are symmetrical and arranged, preferably on a common coreas indicated by the dashed lines, in such manner that coils 25, 26, 29and 30 are magnetically additive with respect to coils 27, 28, 31 and82. When, therefore, the amplified phantom current enters the primarywinding of transformer 20, the secondary thereof causes flow of currentin one direction in wires 1 and 2 and in the opposite direction in wires3 and 4. The above described apparatus constitutes a repeater for thephantom circuit, which repeater derives phantom current from the line bytrans, former 21, amplifies this current by means of the device 40 andimpresses the amplified current on the line by means of transformer 20.None of the current from transformer 20 enters transformer 21 underconditions of proper balance of the phantom circuit be cause the points50 and 51 in both. pair of Wires are of like potential relative to theelectromotive forces impressed on the wires by the symmetrical coils oftransformer 20. Transformer 21, in other words, is conj to transforn'ier20. Although the amplifying device 40 is described in the presentembodiment of the invention as h ring its input circuit associated withthe shunt trans former 2'1 and its output circuit with the seriestransformer 20, there is no objection from a theoretical standpoint toan arrangement associating the input side of device 40 with the seriestransformer 20 and the outputside, with the shunt transformer 21.

In case it is desired to provide repeaters also for the side circuits,transformers 15 may serve as the input "ansformer of the side repeaters.The drawing shows a singleelement two-way repeater of well known typefor each side circuit, each repeater comprising an amplifying device l0whose input circuit is associated with transformer 15 and whose outputcircuit is connected to the coils 10 and 11 of the primary winding ofthe output transformer 5. The secondary winding of this transformercomprises coils 6 to 9 inclusive, inserted into the line wires, one oneach side of points 50 and 51. The connection of coils 6 and 7 is suchthat they are magnetically additive to coils 8 and 9 when traversed byside circuit current so that this transformer impresses side current onthe line, when its primary receives current from the device 40.

Each of the side circuit repeaters operates by shunting part of the sidecurrent through its transformer 15, amplifying this current in device l0and returning the same, amplilied, to the line conductors by transformer5. Transformers 5 and 15 are conjugate under proper conditions balanceso that current from one does not enter the other.

it should be noted that there is no interference between the phantom andside circuit apparatus. The phantom transformers are unresponsive toside current, and the side current transformers to phantom current,provided always, that proper balance is maintained. rrlt-houghtransformers are used in the present embodiment of the invention toprovide the side circuit neutral points 52 and 53, it is readilyunderstood that any other suitable devices may be used for this purpose,as for example, inductance coils.

The line conductors are metallically con tinuous through the repeatercircuits and therefore transmit direct current or low frequencyalternating current, such as is commonly used for signaling. Condensersu; and 17 are inserted into the primary windings of transformers 15 toprevent these windings from short circuiting the signaling currents. Thinvention thus provides for normally continuous signaling paths throughthe repeater installation. To make the arrangement particularly adaptedfor composited systems, retardation coils l8 are bridged across theinput transformer 15 and 21. The condensers and retardation coilsconstitute filters, which provent the low frequency ringing current, andthe pulsating telegraph current from entering the repeaters and thuscausing interference in the telephone circuits. It is readily understoodthat each telegraph or other signaling circuit may be formed of one lineconductor and ground or may be constituted of two line conductors, asusual in the art.

Although only one form of apparatus and circuits embodying the inventionis shown and described herein, it is readi y understood that variousmodifications and changes may be made therein within the scope of thefollowing claims, without departing frmn the spirit and scope of thisinvention.

What is claimed is:

1. ln combination, a plurality of electrical conductors, conductivelycontinuous side circuits each formed of a portion of said conductors andadapted for the transmission of direct current, a phantom circuitforn'ied of said conductors, a repeater intermediate the ends of saidconductors, said repeater having input and output sides and means foroperatively associating both sides of said repeater with said conductorsin their phantom circuit relation.

2. In combination, a plurality of electrical conductors, circuits oversaid conductors normally continuous to direct current, a phantom circuitover said conductors, a repeater intermediate the ends of saidconductors, said repeater having input and output sides and meansassociated with said conductors for operatively associating both sidesof said repeater with the phantom circuit.

In combination, a plurality of continuous conductors arranged to form aphantom circuit, a translating}; device intermediate the ends of saidconductors, means for associating one side of said device with saidcircuit in shunt relationship and means for associating the other sideof said device with said circuit in series relationship. I

4. In combination, a plurality of electrical conductors arranged to formside and phantom circuits, a repeater, and means for operativelyassociating said repeater with said phantom circuit, said meanscomprising a transformer having the convolutions of one winding in theside circuit conductors.

5. In combination, a plurality of electrical conductors arranged to formside and phantom circuits, a translating device having one sideassociated with said phantom circuit in shunt relationship and atransformer for associating the other side of the device with saidcircuit in series relationship the convolutions of one side of saidtransformer being inserted into the side circuit conductors.

6.111 combination, a plurality of electrical conductors arranged to formside and phantom circuits, a translating device, coils in said sidecircuit conductors for associating one side of said device with saidphantom circuit in series relationship, and electrical connections topoints on said conductors intermediate said coils bridging the otherside of said device across said phantom circuit.

7. In combination, a plurality of electrical conductors arranged to formside and phantom circuits, a translating device, coils in said sidecircuit conductors for associating one side of said device with saidphantom circuit, and means having conjugate relation to said coils forassociating the other side of said device with said circuit.

8. in combination, a plurality of conductively continuous lineconductors arranged to form a phantom circuit, a repeater for saidcircuit and comprising input and output circuits, a device bridgedacross said conductors for associating one of said repeater circuitswith said phantom circuit, a transformer conjugate to said device andcomprising a winding connected in series with said conductors forassociating the other repeater circuit with the phantom circuit.

9. In combination, a phantom group comprising two pairs of lineconductors arranged to form a phantom circuit, a repeater for thephantom circuit, a transformer for associating one side of said repeaterwith said circuit in series relation ship, said transformer comprisingtwo coils in each line conductor all of said coils being magneticallyadditive, when traversed by phantom circuit current and a secondtransformer having one winding connected to each conductor intermediatethe coils therein for associating the other side of the repeater inshunt with said line, and in conjugate relationship to said firsttransformer.

10. The combination with a plurality of electrical conductors arrangedto form two side circuits and a phantom circuit, of a repeater in eachside circuit, comprising a circuit bridged across the corresponding sidecircuit, a repeater for said phantom circuit comprising an amplifier andinput and output circuits therefor, means for bridging one of saidlast-mentioned circuits across said circuits of said side circuitrepeaters, and means for associating the other of said circuits withsaid phantom circuit in series relationship thereto.

11. In combination, a plurality of line conductors arranged to form aphantom and two side circuits, a repeater for each circuit, eachrepeater comprising an input and an output circuit, means for each siderepeater for bridging one of its circuits across the corresponding sidecircuit, means for the phantom repeater for bridging one of its circuitsacross the first mentioned means, and means traversed by both phantomand side circuit currents and selectively responsive thereto, forassociating the other circuit of each repeater with the line conductors.

12. In combination, a phantom group comprising four conductors arrangedto form a phantom and two side circuits, a. transformer for each sidecircuit comprising a pair of coils in series with each conductor of theside circuit, the coils in one conductor of each side circuit beingmagnetically opposed to the coils in the other conductor with respect tophantom current but additive with respect to side circuit current, asecond transformer for each side circuit conjugate to said firsttransformer and having one winding connected across the correspondingside circuit conductors at points therein intermediate said pairs ofcoils, an amplifying device for each side circuit and operativelyassociated with the shunt and series transformer thereof, a thirdtransformer having a pair of coils in each side circuit conductor, thecoils in each side circuit being magnetically opposed relative to sidecircuit current and additive relative to phantom currents, a fourthtransformer bridged across the midpoints of the first transformer andhaving conjugate relationship to said third transformer, and anamplifying device operatively associated with said third and fourthtransformers.

13. A transmission system comprising a plurality of circuits, one ofsaid circuits being a phantom, a line conductor traversed at each pointby current in said phantom and another of said circuits, and a repeaterfor said phantom circuit associated with said conductor intermediate itsends.

-. 14. In a composite transmission. system, a plurality of continuousline conductors, a plurality of circuits including a phantom circuitOver said conductors, a signaling. circuit associated with one of theconductors comprised inv said phantom circuit each point of saidconductor beingtrayersed. by current in said phantoinand said signalingcircuits, a repeater for said: phantomucircuit, and means forpreventingthe signaling current from causing interference in saidplurality of circuits.

15.In combination, a plurality-of .line conductors a phantom circuitcomprising said conductors, a repeater, and meansiinterposed in saidline....conductors between the terminals thereof foroperativelyassociating said repeater with said phantom circuit, saidmeans being connected. to the conductorszsqzasism-permit the flow oi direct current therethrough.

16. In combination, a phantom group of conductors "comprising side andphantom circuits, a transformer having tl1ec 0nv0 lutions ofone Windingin-series in said conductors and traversed "by current in both :side andphantom; (circuits, a translating device, and qafsecond winding for saidtransformer having its terminals associated with said translatingdeviceand having its 'convolutions s0 related to those ofithevotherWinding that said translating device is operatively associated only withsaid phantom circuit.

In testimonyqvhereof, I have signed my name to, this specificationthis23rd day of l/Iay, $1919.

OTTO B. BLACKVVELL.

